Temperature control is an important consideration in many spacecraft applications. In one spacecraft application, structures must be protected against temperature extremes of heat or cold that could cause the structure to warp or otherwise become damaged. Even slight temperature-induced deformation may cause a sensitive structure to become inoperable.
In another spacecraft application, some devices must be maintained at extremely low operating temperatures. For example, many electronic components that process infrared signals are operated at cryogenic temperatures (e.g., 77K or less) to avoid spurious heat-related signals or because the instrumentation functions properly only at such low temperatures. At higher temperatures, the devices may become inefficient or cease operation entirely.
Such devices requiring low temperature are usually provided with their own cooling capability such as a closed-cycle refrigerator or cryostat. The more heat that the refrigerator must remove, the larger it is and the more power it consumes. Additionally, the more heat leakage, the slower the initial cool-down of the cooled device, and the greater the cooling capacity required to maintain the cooled device at the operating temperature.
For these reasons, the temperature-sensitive structures and cooled devices are carefully insulated as well as internally cooled. The state-of-the-art insulation for cooled devices operating in space is “multi-layer insulation”, sometimes termed MLI. Typically, the MLI is formed of alternating layers of polymeric radiation shield and low-thermal-conductivity material such as a polymeric mesh. The radiation shield reflects radiated heat, and the low-thermal-conductivity material separates the layers of radiation shield and also prevents conductive thermal transport through the MLI. In most applications, the MLI includes 15-70 or more layers. To insulate the device, the layers are individually applied by hand layup in a serial manner, and the layers are joined together appropriately. This application is a slow, costly process.
The MLI may be effective in insulating the device, but it is extremely difficult and time-consuming to apply correctly. Regardless of the care and skill of the technicians who apply the MLI, a wide variation in the final insulation performance is measured from insulated device to insulated device. As a result, even after careful application precisely following the established best assembly practices, the measured thermal performance of the insulated device may be insufficient for the required application. At that point, it is necessary either to add more insulation or to remove the applied insulation and redo the insulation, and even after reworking the insulation the performance may be inadequate. Additionally, thermal shorts that provide local high-heat-flow paths are often observed in insulated hardware, particularly at sharp corners but potentially anywhere, in the normally handled device. The thermal shorts may appear in an insulated device that initially has proper performance, but later develops the heat-leakage problem as a result of routine handling. Thermal shorts also may result from dropping or impacting the insulated hardware. The insulating of hardware using MLI is time consuming and expensive, and even then achieves somewhat unpredictable results.
There is a need for an improved approach to insulating space-operated hardware that achieves a level of insulation performance equivalent to or better than that of current MLI, but at reduced cost and with greater predictability and reliability. The present invention fulfills this need, and further provides related advantages.